1. Field of the Invention
The present invention generally relates to chip scale packaging and more particularly to a chip scale power converter package having an inductor substrate.
2. Description of Related Art
It is well known to include a discrete inductor on the printed circuit board when implementing a power converter circuit. For example, the Analogic™TECH 1 MHz 400 mA Step-Down Converter (AAT1143) requires the use of a discreet inductor. Power converters implemented in this way suffer the disadvantages of having higher component cost and of requiring more printed circuit board space.
Discrete inductors co-packaged with power ICs and other components are also well known. For example, the LTM®4600 DC/DC power converter available from Linear Technology Corporation of Milpitas, Calif., includes a built-in inductor in a 15 mm×15 mm×2.8 mm package. The package disadvantageously uses valuable printed circuit board space.
It is further known to dispose an inductor on top of an integrated circuit die such as a power converter integrated circuit die. For example, power converters available from Enpirion of Bridgewater, N.J., include a MEMS-based inductor having a thick electroplated copper spiral coil sandwiched between two planar magnetic layers and disposed over an integrated DC-DC converter. To achieve high inductance, a large die is required resulting in a high cost and a large package. Furthermore, complex processing is necessary in order to fabricate the planar magnetic layers.
There is therefore a need in the art for a chip scale power converter that overcomes the disadvantages of the prior art. There is a need for a low cost chip scale power converter that does not require an external inductor. There is a further need for a chip scale power converter having an optimized interconnection between the power IC and the inductor for minimized parasitics, improved performance and high reliability.